1. Field of the Invention
This invention relates to a light source unit including a light source portion with an LED (light emitting diode) element, and a heat radiation portion connected to the light source portion.
2. Description of the Related Art
JP-A-2004-327138 discloses a light source unit using an LED. The light source unit is composed of a mounting board for mounting an LED chip thereon, and a case for housing the mounting board therein, the case including bottom portion and a cylindrical portion formed integrally. Plural LED chips are mounted on the mounting board, back of which being tightly contacted via a thermally conductive insulating material by an adaptor of aluminum etc.
The plural LED chips are connected in series parallel via a pattern formed on the mounting board and connected to electrodes at the center of the mounting board. The mounting board is supported by the case by plugging the electrodes into a socket of the case. JP-A-2004-327138 mentions the effect that most of heat generated from the LED chips can be transferred through the mounting board with the LED chips, thermally conductive insulating material and the adaptor to the case, and then radiated externally through the cylindrical portion of the case,
However, the light source unit of JP-A-2004-327138 is constructed such that its components, i.e., the mounting board, the thermally conductive insulating material, the adaptor and the case are tightly contacted one another, and, therefore, it has the problem that relatively large stress is generated among the components when the components are thermally expanded by heating during operation. In addition, heat is positively transferred to the case being exposed outside and, therefore, external parts contacting the case may be heated and it is dangerous for a user to touch directly the case with his hand when handling the light source unit.